Wideband hybrid system

ABSTRACT

An input diplexer separates wide frequency range signals by frequency to provide, at a plurality of outputs, signals within different narrow frequency bands. A plurality of quadrature hybrids are adapted so that each hybrid achieves equal power division and 90* relative phase shift with low distortion over one of the narrow frequency bands. A hybrid is coupled to each output of the input diplexer. Output diplexers are coupled to the two outputs of each of the hybrids to combine the power divided narrow frequency band signals into two wide frequency band signals of substantially equal power and of 90* differential phase.

United States Patent Foldes Oct. 23, 1973 l WIDEBAND HYBRID SYSTEMPrimary Examiner-Rudolph V. Rolinec Assistant Examiner-Marvin Nussbaum:Pt Fld M t l,C d Inventor e er on ma ana a W Att0rneyEdward J. Nortonet al. [73 Assignee: RCA Corporation, New York, NY.

[22] Filed: Jan. 5, 1973 [57] ABSTRACT [21] APPL 321,469 An inputdiplexer separates wide frequency range signals by frequency to provide,at a plural ty of outputs, signals within different narrow frequencybands. A [52] US. Cl 333/6, 333/11, 333/21 A, plurality of quadrature hi are adapted so that 333/29 333/31 333/70 R1 333/73 w each hybridachieves equal power division and 90 rel- [51] f Cl H16, H18, Help /12ative phase shift with low distortion over one ofthe [58] Field ofSearch 333/6, 11, 21 R, narrow frequency bands. A hybrid i coupled toeach 333/21 A, 31 R, 31 A, 70 1 73 R, 73 w output of the input diplexer.Output diplexers are coupled to the two outputs of each of the hybridsto com- [56] References W 1 bine the power divided narrow frequency bandsignals UNITED STATES PATENTS into two wide frequency band signals ofsubstantially 2,727,141 12 1955 Cheek 333/29 x equal Power anddifferential P 3,056,096 9/1962 Vane 333/73 W X 5 Claims, 2 Drawing gu IQUADRATURE 2) I r- 1 1 49 1 3O 23 OUAR'ATURE ,35 1v I 1 2 1 46 PWR 1 Z'l,230 373 i c0111; f 0, QUARATURE 1 d5 1 L 25, i L 39 3 9b 43 0.0. '27 U1'" "1 \,27c 3 5 1 i 1 9 '1 9 9C 1 2 I 1 2 PWR 243 QUADRATURE 38 frh PWRI 8 1 mv. I711 3011 111111110 1 f COMB 1 3 4 I 1 34 i 3 4 1 2 f4- 1 1 4-5 l l 32!] v l L l E 1 l Q L EZELJ llu PATENTEDnm 23 ms SHEET 18F 2WIDEBAND HYBRID SYSTEM BACKGROUND OF THE INVENTION This inventionrelates to hybrids and more particularly to a polarizer using a systemof hybrids for achieving 90 differential phase shift and power splittingover a wide band of frequencies with low amplitude and phase error.

It is desirable for achieving circular polarization that the signals fedto the orthogonally polarized antenna radiating element be at phasequadrature or 90 difference in relative phase and that the power beexactly divided. A practical way of achieving this with low loss is bymeans of a short slot hybrid. Although these short hybrid slot deviceshave had humps put at the center of the short slot region or the crosssectional width made smaller near the slotted region to achievebroadband operation, these hybrid structures remain relatively narrowband devices. When one of these devices is operated over a widefrequency band such as for example from 3,700 to 4,200 MHz (as insatellite communication systems), phase error of over is produced atsome frequencies in the band. Consequently, relatively high axial ratiosoccur when the outputs of one ofthese are applied to the elements of anantenna. Wideband polarizers capable of achieving axial ratios in theorder of 0.25 to 0.5 db are required over these above frequencies insatellite communication systems. This has heretofore not been achievedover such widebands using hybrids.

Briefly, according to the present invention substanequal in amplitude,90 different in relative phase and no output power is coupled at 1 orreflected back to I Further, the purpose of the circuit is that theterminal I of diplexer 11 and the terminal of diplexer 11a beinterchangable and simultaneously useful. All of the above functions aremaintained in the f through f frequency band. Circular polarization isachieved by coupling the output at terminal 0 to one terminal 9a of anorthogonal coupler 9, for example, and the other output at terminal 0 iscoupled to an orthogonally oriented terminal 9b of coupler 9. If theseoutputs at O, and 0 are equal in power and at phase quadrature purecircular polarization is achieved. The coupling to the orthogonallyoriented terminal 9b may require a rotation of the polarization attitude90. This rotation may be accomplished by a twisted waveguide section(rotator) 8 located in the coupling lead between terminal 0 and terminal9b.

The input signal I at frequencies f, to f is divided on the basis offrequency by diplexer 11 into four frequency bands f to f f to f f,, tof, and f', to f The diplexer 11 is made up of a power divider 13followed by a plurality of band-pass filters 15, 16,17 and 18. The

power divider l3 splits the input signal power into, for example, foursignals of equal power and couples these separate signals to separatefilters 15, l6, l7 and 18.

tially lower amplitude and phase error is achieved for 1 providing equalpower division and 90 relative phase shift between the power dividedoutputs by the use of a first diplexer for subdividing the signals byfrequency into subfrequency bands and by coupling the narrow frequencyband signals to separate hybrids. The separate hybrids are each adaptedto provide at their two separate outputs, power division and 90 relativephase shift between the power divided signals over the particular narrowfrequency band coupled thereto with minimum amplitude and phase error.That one of the two outputs from each of the separate hybrids havingsubstantially identical phase is coupled to a second diplexer forcombining the narrow band signals to a first Wideband output. The secondoutput from each of the separate hybrids is coupled to a third diplexerfor combining the 90 relative phase shifted nar'row frequencybandsignals to a second wideband output.

A more complete description of the subject invention follows inconjunction with the following drawings wherein:

FIG. 1 is a schematic diagram ofa Wideband hybrid system and a polarizersystem using the same according to the presentinvention.

FIG. 2 is a perspective view of a portion of a wideband hybrid systemshownin FIG. 1 with a portion of the top walls removed. g

Referring to-the block diagram of- FIG. 1, there is shown a Widebandhybrid system 10 consisting of two diplexers 11 and 11a at the input andtwo output diplexers 41 and 43 with four short slot quadrature hybrids21, 23, 25 and 27 coupled therebetween. The purpose of the circuit is todivide the input power fed to the input terminall, of diplexer 11 intotwo parts occurring at the output terminals 0 of diplexer 41 and 0 ofdiplexer 43 in such a way that the output powers are The band-passfilter 15 is selected to pass those frequencies within the f, to ffrequency band. Similarly,

band-pass filters l6, l7 and 18 are selected to pass the frequency bandsf to f f; to f, and f, to f, respectively.

A plurality of hybrids 21, 23, 25 and 27 equal to the number ofband-pass filters is provided. The hybrid 21 is adapted topro'vide equalpower division of the input signal with differential phase shift betweenthe power divided signals. The hybrid 21 is designed to accomplish thiswith minimum phase'and amplitude error between its two output ports overthe frequencies of from f, to f,. The output of band-pass filter 15 iscoupled via lead 29 to input terminal 21a of hybrid 21. The hybrid 23'is similarly I adapted to operate as a 90 differential phase shiftingpower dividing coupler but with minimum phase and amplitude error overthe frequencies from f to f,,. The output of band-pass filter 16 iscoupled via lead 30 to terminal 23a of hybrid 23. The hybrid 25 issimilarly a 90 differential phase shifting power dividing coupler whichis adapted to operate 'with'minimum phase and amplitude error over thefrequencies from f, to f,. The output of band-pass filter 17 is coupledvia lead 31 to terminal 25a of hybrid 25. The hybrid 27 is a 90differential phase shifting power dividing couplerwhich isadapted tooperate with minimum phase and amplitude error over the frequencies fromf to f The output of band-pass filter 18 is coupled via lead 32 toterminal 27a of hybrid 27. The hybrids 21, 23, 25 and 27 may each'beshort slot hybrids as described, for example, by Riblett in US. Pat.Nos.

2,739,287 and 2,739,288. Basically, each of these short plexer 41includes band-pass filters 45, 46, 47 and 4s; Bandpass filter 45 isadapted to couple only those signals with low attenuation between thefrequencies off; to f Similarly, band-pass filter 46 is adapted to passthe frequencies off to f Band-pass filter 47 is adapted to pass thefrequencies betweenf to f with low attenuation and band-pass filter 48is adapted to pass frequencies between f. to f with low attenuation. Inthe diplexer 41 the outputs of band-pass filters 45, 46, 47 and 48 areeach coupled to a power combiner 49 wherein the signals at frequenciesfrom f to f are combined to provide an output at terminal 0,. Diplexer43 is similarly arranged comprising band-pass filter 55 covering thefrequency range from f to f band-pass filter 56 covering the frequencyrange from f to f band-pass filter 57 covering the frequency range fromf tof., and band-pass filter 58 covering the frequency range from f, tof All the output power at the band-pass filters 55 through 58 arecombined at power combiner 59 to provide a single output at outputterminal of diplexer 43.

The power divided signal at terminal 21b of hybrid 21 is coupled vialead 33 to band-pass filter 45 in diplexer 41. The equal power 90 phaseshifted signal at terminal 210 of hybrid 21 is coupled via lead 35 toband-pass filter 55 of diplexer 43. The one half power output signal atterminal 23b of hybrid 23 is coupled via lead 37 to band-pass filter 46of diplexer 41. The equal power 90 relative phase shifted signal fromhybrid 23 at terminal 23c is coupled via lead 38 to band-pass filter 56of diplexer 43. The half power output signal from hybrid 25 at terminal25b is coupled via lead 39 to bandpass filter 47 of diplexer 41. Theequal power and 90 relative phase shifted signal at terminal 250 ofhybrid 25 is coupled via lead 40 to band-pass filter 57 of diplexer 43.The half power output signal at terminal 27b of hybrid 27.is coupled toband-pass filter 48 of di plexer 41 via lead 36. The equal power 90differential phase shifted signal at terminal 27c is coupled via lead 34to band-pass filter 58 of diplexer 43.

In the operation of the device described in FIG. 1, the input signals 1of frequencies from f tof which cover the operating frequency band ofthe system are coupled to the input power divider 13 wherein thesesignals are divided into four equal power sections and coupled to therespective filters 15, 16, 17 and 18. The filter passes frequencies fromf to f to short slot hybrid 21. At the hybrid 21 the f to f frequencysignals are equally power divided and with one portion undergoing zeroor reference phase shift to terminal 21b and the other portionundergoing 90 differential phase through the short slot 22 in hybrid 21to terminal 210.

The output at terminal 21b is coupled to band-pass filter 45 in diplexer41 via lead 33. The 90 differential phase shifted signal at terminal 21cis coupled via lead 35 to band-pass filter of diplexer 43. Similarly,those signals at frequencies from f to f;, are coupled to short slothybrid 23 and power divided such that those signals at the referencephase at hybrid terminal 23b are coupled to band-pass filter 46 ofdiplexer 41 and the 90 differential phase shifted signals at terminal23c are coupled to band-pass filter 56 of diplexer 43. Those signalsbetween frequencies f to f are coupled to short slot hybrid 25 with theone half power output at terminal 25b at reference phase coupled toband-pass filter 47 of diplexer 41 and those half power signalsundergoing 90 differential phase shift being coupled out of terminal 25cto band-pass filter 57 of diplexer 43. The signals at frequenciesbetween f and J2, are coupled out of band-pass filter 18 to short slothybrid 27. The output signals at reference phase at terminal 27b ofhybrid 27 are coupled to band-pass filter 48 of diplexer 41 and thedifferential phase shifted signals at terminal 27c are coupled toband-pass filter 58 of diplexer 43. As can be seen by reviewing theabove, those signals which undergo the 90 additional phase shift arecoupled to the diplexer 43 and the other signals of equal power but ofreference phase are coupled to diplexer 41. The signals at the band-passfilters 45 through 48 are combined at power combiner 49 to provide onehalf the total output power at the reference phase at terminal 0,. Theband-pass filters 55 through 58 are coupled to power combiner 59 whereinthe other half of the total power at the frequencies from f tof arecombined and applied to the output terminal 0 The power at terminal 0should approximately equal the power at terminal O and be at 90 relativephase to the phase of the signal at terminal 0,.

A nearly circular polarized wave with a relatively low axial ratio ofpowers at the two terminals is achieved for example by coupling theoutput at terminal 0 to one terminal 9a of orthogonal coupler 9 and bycoupling the other output at terminal 0 to terminal 9b of the orthogonalcoupler 9 via attitude rotator 8. The orthogonal coupler 9 may becoupled at terminal 9c to a radiating horn antenna, not shown, wherebythe circular polarized waves are radiated or received. The orthogonalcoupler 9 may be a square section of waveguide (not shown) with theterminals 90 and 9b oriented to excite the output signal at terminal 0in for example a TE mode and to excite the output signal at terminal 0in the orthogonal TE mode. Metal irises (not shown) can be placed acrossthe input of terminal 90 orthogonal to the electric field in the TE. toprovide isolation of the two terminals 9a and 9b. A typical waveguideorthogonal coupler may be like that shown in FIG. 8 and described inconnection therewith in U. S. Pat. No. 3,569,870 issued to Peter Foldes.

Input signals applied to terminal 1 in FIG. 1 undergo similar operationto that described above for input signals applied to diplexer 11. Inputsignals applied to terminal 1 of diplexer 11a are power divided atdivider 13a with those signals from frequency f tof being coupledthrough filter 15a and lead 290 to terminal 21d of hybrid 21. Similarly,those signals at frequencies f to f at divider 13a are coupled throughfilter 16a and lead 30a to terminal 23d of hybrid 23. Signals atfrequencies f tof, at divider are passed through filter 17a and lead 31ato terminal 25d of hybrid 25. Signalsat frequenciesf, tof at divider 13aare passed through filter 18a and lead 32 to terminal 27d of hybrid 27.The operation of the hybrids 21, 23, 25 and 27 and diplexers 41 and 43is similar to that described above with the output at terminals 0 and 0being of equal power at 90 relative phase but in this case the output atterminal 0 undergoes the additional 90 phase shift and the output atterminal 0 is at reference phase. This is due to the fact that thesignals which are ultimately coupled to diplexer 41 are coupled throughthe slots in each of the hybrids 21, 23, 25 and 27.

As mentioned previously, it is desirable that the device be reciprocal.It can be seen that by making the power dividers and power combinersidentical by having them both with the filters at the input and outputterminals of the hybrids, reciprocal operation is provided. For example,signals applied at output terminal 0, of diplexer 41 can also undergothe frequency division of the signals corresponding to f to f ,f to f ,ftof, andf, to f, and be applied to the corresponding hybrids 21, 23, 25and 27. Since the hybrids are symmetrical, the two output signals fromeach of the hybrids are of equal power with 90 relative phase shiftbetween the two output signals. Diplexer 11 in the example combines thesignals of reference phase and the diplexer 11a combines the signalshaving the additional 90 phase shift. Also, it is necessary that thesehybrids 21, 23, 25 and 27 at either end see a similar match. This isprovided by having similar band-pass filter sections coupled at eachterminal of a given hybrid.

Turning to FIG. 2, there is illustrated the construction of a portion ofsuch a wideband hybrid system. Only two diplexer sections and themultiple hybrid section is illustrated in the assembly 61 shown sincethe remaining two diplexer sections (not shown) of the assembly 61 areidentical in construction to the first two diplexers. Waveguide assembly61 as shown in FIG. 2 is made up of two waveguide sections 63 and 64each sharing a common narrow wall 65. The waveguide section 63furtherincludes-broad walls 67 and 69 and narrow wall 70 opposite common wall65. Thewaveguide section 64 includes opposite broad walls 71 and 73 andnarrow wall 75 opposite common wall 65. The top walls 67 and 71 areformed by one continuous conductive plate and the bottom walls 69 and73' are formed 81 at these apertures. At the hybrids 92, 93, 94 and 95the signals are power divided with the outputs from the two outputterminals of each hybrid being substantially 90 out of phaseand ofsubstantially equal power. The outputs from the hybrids 92, 93, 94 and95 are coupled to a structure (partly shown) which is a continuation ofwaveguide sections 63 and64. The remaining structure by one continuousconductive plate. The waveguide section 63 is power divided into fourequal rectangular waveguide sections by three plates 77, 78 and 79,which are placed parallel to each other. and parallel to walls 69 and67. Similarly, plates 81, 82 and 83 are placed within waveguide section64. The input signal applied to waveguide 63 is then power divided by afactor of four into separate waveguide sub-sections formed between theplates 77, 78 and 79 and between plate 77 and wall 67 and between plate79 and wall 69.

The input signals coupled to the input of waveguide section 64 are powerdivided between the plates 81, 82

and 83 and between the plate 81 and wall 73 and be-- tween broad wall.71 and plate 83. By placing tuning stubs or irises 91 in thesub-sections between the plates and the broad walls, the waveguidesub-sections formed between the plates and between the plates and thebroad walls of thewaveguide can be 'made to pass different frequenciesand'thus'ly pro'vide frequency separation. In the arrangement shown inFIG. 2, the irises 91 are placed within thesesections to form band-passfilters forpassing, for example, at the top waveguide sub-section 63aformed between wall 67 and plate 77,

' a band-pass filter at f, to f frequencies. Similarly, the

sub-section 63b formed between the plates 77 and 78 passes frequenciesfrom f, to f;,, the sub-section 63c between plates 78 and 79 passesfrequencies from f to f and the sub-section 63d formed between plate 79and wall 69 passes frequencies from f to f Similarly, the band-passfilters at frequencies f, to f f to f f to f, and f, to f are providedby thewaveguide sub-sections 64a, 64b, 64c and 64d having appropriatelyplaced is similar to that shown at the input but is symmetricallyarranged so that the outputs of the hybrids are coupled to the band-passfilter sections includingthe plates and irises and the output of'thefilter sections is coupled to the undivided waveguide section to form acombiner. The filter section coupled to each terminal of each hybrid ismade substantially the same.

Numerous and varied other arrangements within the sphere and scope ofthe principle of the invention will have occurred to those skilled inthe art. The general principles of the invention are, for example,readily applicable to systems employing two or more hybrids andcorresponding band-pass filters and power dividers. Power division canbe up to any n number of sections with nband-pass filters and n hybridsto achieve the desired minimum phase and amplitude error through such'hybrids. In the configuration using only two such hybrids,-"fourdiplexers' and an orthogonal c0uple'r,an

axial ratio on the order of 0.35 db is achieved in the 3,700 to 4,200MHZ 'fre quencyjband.

What ,is claimed isi v 1. A system for providing substantially equalpower splitting and 909. relative phaseshiftof power divided signalsover a given relatively wide band of frequencies with reduced amplitudeand phase error comprising:

afirst diplexer responsive to signals of said given wide band .offrequencies at its input for separating said signals by frequency toprovide at a plurality of first diplexer output terminals signals withindifferent narrow frequency bands where the sum of aid narrowfrequency-bands covers the frequency spectrum of said given wide band offrequencies, plurality of quadrature hybrids, each hybrid coupled to adifferent one of said plurality of first diplexer output terminals andadapted to provide equal power splitting to first and second hybridoutput terminals with signals at the first hybrid output terminalundergoing less phase shift than the signalsat the second hybrid outputterminal with minimum error over the coupled relatively narrow frequencyband,

-a second diplexer coupled to said first hybrid output terminal 'of eachof said plurality of hybrids and being'responsive to said signals withineach of said 7 narrow frequency bands for providing at the seconddiplexer output terminal wide frequency band signals of a given powerlevel and phase,

a third diplexer coupled to the second hybrid output terminal of each ofsaid plurality of hybrids and being responsive to said signals withineach of said narrow frequency bands for providing at the third diplexeroutput terminal said wide frequency band signals of a power levelsubstantially equal to said given power level and at 90 relative phaseto said given phase.

. 2; A wideband polarizer for providing circularly polarized waves fromlinearly polarized waves over a given wide band of frequencies with lowaxial ratio comprising:

a first diplexer responsive to the linearly polarized signals over thegiven wide band of frequencies at its input for separating said linearlypolarized signals by frequency to provide at a plurality of firstdiplexer output terminals linearly polarized signals within differentnarrow frequency bands where the sum of said narrow frequency bandscovers the frequency spectrum of said given wide band of frequencies,

a plurality of quadrature hybrids, each hybrid coupled to a differentone of said plurality of first diplexer output terminals and adapted toprovide equal power splitting to first and second output hybridterminals with linearly polarized signals at the first hybrid outputterminal undergoing 90 less phase shift than the linearly polarizedsignals at the second hybrid output terminal with minimum error over thecoupled relatively narrow frequency band,

a second diplexer coupled to said first hybrid output terminal of eachof said plurality of hybrids and being responsive to said linearlypolarized signals within each of said narrow frequency bands forproviding at the second diplexer output terminal wide frequency bandlinearly polarized signals of a given power level and phase, .7

a third diplexer coupled to the second hybrid output terminal of each ofsaid plurality of hybrids and being responsive to said linearlypolarized signals within each of said narrow frequency bands coupledthereto for providing at the third diplexer output terminal said widefrequency band linearly polarized signals of a power level substantiallyequal to said given power level and at relative phase to said givenphase,

an orthogonal coupler having a first terminal coupled to the seconddiplexer output terminal and an orthogonally oriented second terminalcoupled to the third diplexer output terminal and responsive to linearlypolarized signals for providing circularly polarized waves over saidwide band of frequencies with substantially low axial ratio.

3. The combination claimed in claim 2, wherein said 4. The combinationclaimed in claim 3 wherein all of the band-pass filters coupled to agiven one of said hybrids are substantially identical.

5. The combination claimed in claim 2, wherein said hybrids are shortslot hybrids. Y

1. A system for providing substantially equal power splitting and 90*relative phase shift of power divided signals over a given relativelywide band of frequencies with reduced amplitude and phase errorcomprising: a first diplexer responsive to signals of said given wideband of frequencies at its input for separating said signals byfrequency to provide at a plurality of first diplexer output terminalssignals within different narrow frequency bands where the sum of saidnarrow frequency bands covers the frequency spectrum of said given wideband of frequencies, a plurality of quadrature hybrids, each hybridcoupled to a different one of said plurality of first diplexer outputterminals and adapted to provide equal power splitting to first andsecond hybrid output terminals with signals at the first hybrid outputterminal undergoing 90* less phase shift than the signals at the secondhybrid output terminal with minimum error over the coupled relativelynarrow frequency band, a second diplexer coupled to said first hybridoutput terminal of each of said plurality of hybrids and beingresponsive to said signals within each of said narrow frequency bandsfor providing at the second diplexer output terminal wide frequency bandsignals of a given power level and phase, a third diplexer coupled tothe second hybrid output terminal of each of said plurality of hybridsand being responsive to said signals within each of said narrowfrequency bands for providing at the third diplexer output terminal saidwide frequency band signals of a power level substantialLy equal to saidgiven power level and at 90* relative phase to said given phase.
 2. Awideband polarizer for providing circularly polarized waves fromlinearly polarized waves over a given wide band of frequencies with lowaxial ratio comprising: a first diplexer responsive to the linearlypolarized signals over the given wide band of frequencies at its inputfor separating said linearly polarized signals by frequency to provideat a plurality of first diplexer output terminals linearly polarizedsignals within different narrow frequency bands where the sum of saidnarrow frequency bands covers the frequency spectrum of said given wideband of frequencies, a plurality of quadrature hybrids, each hybridcoupled to a different one of said plurality of first diplexer outputterminals and adapted to provide equal power splitting to first andsecond output hybrid terminals with linearly polarized signals at thefirst hybrid output terminal undergoing 90* less phase shift than thelinearly polarized signals at the second hybrid output terminal withminimum error over the coupled relatively narrow frequency band, asecond diplexer coupled to said first hybrid output terminal of each ofsaid plurality of hybrids and being responsive to said linearlypolarized signals within each of said narrow frequency bands forproviding at the second diplexer output terminal wide frequency bandlinearly polarized signals of a given power level and phase, a thirddiplexer coupled to the second hybrid output terminal of each of saidplurality of hybrids and being responsive to said linearly polarizedsignals within each of said narrow frequency bands coupled thereto forproviding at the third diplexer output terminal said wide frequency bandlinearly polarized signals of a power level substantially equal to saidgiven power level and at 90* relative phase to said given phase, anorthogonal coupler having a first terminal coupled to the seconddiplexer output terminal and an orthogonally oriented second terminalcoupled to the third diplexer output terminal and responsive to linearlypolarized signals for providing circularly polarized waves over saidwide band of frequencies with substantially low axial ratio.
 3. Thecombination claimed in claim 2, wherein said first, second and thirddiplexers include band-pass filters coupled to the terminals of saidhybrids.
 4. The combination claimed in claim 3 wherein all of theband-pass filters coupled to a given one of said hybrids aresubstantially identical.
 5. The combination claimed in claim 2, whereinsaid hybrids are short slot hybrids.